The invention relates to a counterholding tool for absorbing torque while tightening screws or the like, which includes both an element for grasping the screw nut and a stop.
Such a counterholding tool is required if a screw is to be tightened with high torque. The screw nut is tightly held with the counterholding tool, so that it does not rotate along with the screw.
The counterholding tool generally used is a simple box-end wrench or a monkey wrench. However, if the screw is to be tightened so much that the counterholding tool can no longer be held fast by the muscular strength of a person using it, then the box-end wrench engaging the screw nut must be made to rest in a stationary manner against some arbitrary point. The face of the box-end wrench resting against that point is the "stop" in the sense referred to above.
If the screw is tightened with high torque, for example to 3000 ft-lbs with a crane connection, then the box-end wrench presses so hard against its stationary abutment that it can no longer be removed manually. The pressure exerted by the counterholding tool against its abutment varies depending on the torque applied during the tightening of the screw, the friction existing between the screw nut and that which is located beneath it, and so forth. In any case, when the torque is high applied, the box-end wrench is elastically clamped, with very great forces, between the screw nut on which it is seated and the abutment against which it rests. In order to release it from this clamped condition, a known procedure is to hammer on the wrench with a heavy hammer and thereby to force it out of frictional engagement with the abutment and the screw nut.
The disadvantage here is that the box-end wrench then moves abruptly out of its firmly clamped position, and the direction of its movement is uncontrolled. There is accordingly a great danger that an accident may occur, injuring the workers involved. Objects in the vicinity may also suffer damage as a result.